Packet scheduling in a low-latency optical interconnect with electronic buffers

Optical interconnect architectures with electronic buffers have been proposed as a promising candidate for future high speed interconnections. Out of these architectures, the OpCut switch[1] achieves low latency and minimizes optical-electronic-optical (O/E/O) conversions by allowing packets to cut-through the switch whenever possible. In an OpCut switch, a packet is converted and sent to the recirculating electronic buffers only if it cannot be directly routed to the switch output. In this paper, we study packet scheduling in the OpCut switch, aiming to achieve overall low packet latency while maintaining packet order. We first decompose the scheduling problem into three modules and present a basic scheduler with satisfactory performance. To relax the time constraint on computing a schedule and improve system throughput, we further propose a mechanism to pipeline packet scheduling in the OpCut switch by distributing the scheduling task to multiple "sub-schedulers". An adaptive pipelining scheme is also proposed to minimize the extra delay introduced by pipelining. Our simulation results show that the OpCut switch with the proposed scheduling algorithms achieve close performance to the ideal output-queued (OQ) switch in terms of packet latency, and that the pipelined mechanism is effective in reducing scheduler complexity and improving throughput.